The Reference 6SN7 Thread

[JTbbb]

Wondering something, if someone buys the Tung-Sol 6SN7, 6F8G and 6J5 variants of the same year/plate will they sound the same or still have a variation in sound.

So far seems I'm on team TS and Melz. Not feeling Ken-Rads. RCA smoked glass is ok, but feels too blunted/warm. Thanks.

You need to try some British tubes . Just sayin!

 

[Somatic]

You need to try some British tubes . Just sayin!

Which ones are your favorites? Man this rabbit hole will never end. hehe

 

[ColSaulTigh]

Which ones are your favorites? Man this rabbit hole will never end. hehe

Your wallet will never forgive you.

 

[JTbbb]

Which ones are your favorites? Man this rabbit hole will never end. hehe

Brimar CV1988’s

Drop me a PM

 

[sam6550a]

Wondering what is a good tube tester for beginners? I am looking to test 6SN7, 6F8G and 6J5 variants. Thank you.

The B&K 707 and its variants is a good choice.

 

[mordy]

Wondering what is a good tube tester for beginners? I am looking to test 6SN7, 6F8G and 6J5 variants. Thank you.

Based on readings and discussions on the forums I have arrived at certain truths about tube testers that usually aren't talked about.
The main function of a tube tester is to tell you if a tube is bad.
In our applications many tubes that don't measure so well sound just fine and can last a very long time.
You may not be able to hear any difference between a tube that measures 100% and one that measures minimum good.
Unscrupulous sellers are able to manipulate the tube testers so that they show very good values for marginal or sub marginal tubes.
Some sellers want to talk you into that you need to change the tubes often. The truth is that many tubes can last for years of service - some people report using the same tubes for 20 years and they still have life in them and sound good.
Caveat Emptor - Buyer Beware!

 

[lupoal]

312 is the EIA (Electronics Industry Association) code for Sylvania and 113 means the 13th week (April) of 1961.

Thank you Mordy
is there a place where I can find codes of the different manufacturers? If I remember right each of them use their own code structure and they change it also during the production period… for example I would like to know then what could be a code for a Sylvania made in May 1957… or 1951

I remember I found a web page with these info but… I lost it

 

[OctavianH]

Wondering what is a good tube tester for beginners? I am looking to test 6SN7, 6F8G and 6J5 variants. Thank you.

I use this one and for beginners is good. I bought it cheaper but with latest inflation rates the small increase in price is normal. It has an octal and noval socket and you can make the connections according to the pinout. For 6F8G you'll need an adapter to 6SN7 but I guess you already have one.
https://www.radioelec.com/lampemetr...bes-valves-oeil-magique-xml-352_387-1507.html

And regarding sellers and their measurements, it's exactly like mordy's saying. They measure at different values than your amp's operating point, and some of them are not reporting the right results. These testers need to be calibrated and so on... I have my doubts on all those measurements and indeed, I have a lot of old tubes measuring 60-70% according to the datasheet and they work perfectly for years.

 

[JTbbb]

Based on readings and discussions on the forums I have arrived at certain truths about tube testers that usually aren't talked about.
The main function of a tube tester is to tell you if a tube is bad.
In our applications many tubes that don't measure so well sound just fine and can last a very long time.
You may not be able to hear any difference between a tube that measures 100% and one that measures minimum good.
Unscrupulous sellers are able to manipulate the tube testers so that they show very good values for marginal or sub marginal tubes.
Some sellers want to talk you into that you need to change the tubes often. The truth is that many tubes can last for years of service - some people report using the same tubes for 20 years and they still have life in them and sound good.
Caveat Emptor - Buyer Beware!

Here is the reply I had from a professional tube tester I use. He rebuilds tube amps and tube testers for a living. This is in relation to 5998/WE421A.
But essentially relates to tubes in general.


“The PC/TC figures are pretty much a standard that people use to buy / sell valves to give an idea of their ‘goodness’, but in reality the 421A / 5998s are very high power triodes used mainly in Military applications back in the day, so to be honest for the purposes of matching the valves for your preamp, the PC score is really irrelevant, whether a valve can drive 90mA or 40mA is of no consequence when it is in circuit driving 5/6mA, they will pretty much all work until they become noisy or completely exhausted. A more useful parameter to match against is the TC (transconductance, loosely described as the gain of the valve), so use that as a basis for matching, but again don’t worry unduly, because I think you would be hard pushed to hear the difference between a valve with a TC of 9 or 14, but always good practice to get as close as possible. The main criteria with your amp I would suggest is how noisy they are, as that directly affects the listening experience, old valves can become noisy and microphonic, as you know”.

 

[mordy]

Thank you Mordy
is there a place where I can find codes of the different manufacturers? If I remember right each of them use their own code structure and they change it also during the production period… for example I would like to know then what could be a code for a Sylvania made in May 1957… or 1951

I remember I found a web page with these info but… I lost it

Here is a reference to different EIA code lists for different years:
https://www.ecianow.org/eia-source-codes

As far as I know the EIA codes did not change for manufacturers, but perhaps a code was added when a company would buy another company (?).

Regarding you Sylvania question, a number of companies switched to different date coding systems, or sometimes even having two systems being used at the same time - for example for civilian and military use. Usually the military date code is straight forward - 52-39 would mean 39th week 1952.

Sylvania tubes from the early 50s have two date codes - one on the base of the tube and one on the glass under the tube designation logo. Presumably one code is manufacturing date and the other shipping date - there could be several months discrepancy.
Here is an example - a Motorola 6J5GT tube. The base says 312026 and under the 6J5GT on the glass it says COM.
COM:
C = March (count ABC on your fingers but skip I because it is too easily confused with 1)
0 = 1950
M = maybe the factory

312 is the Sylvania EIA code
026 means 1950 26th week (June)

So the tube was made in March 1950 and shipped in June 1950.

Another example - a FoMoCo 6J5GT tube (Ford Motor Company) has the following codes:
L9M and 312 026.
L = November
9 = 1949
M = factory
312 and 026 as above; in other words both tubes were shipped at the same time but manufactured several months apart.

Tung Sol codes are a complete mystery - it appears that the date codes indicate the end of the warranty period. Sometimes the original tube box will have a date printed, and you may be able to compare it to the date code on the tube base.

Sometimes the date code follows the alphabet but starting in the middle with N being the starting point (January). I have an Arcturus 6N7G tube that says N4 N4 on the base. IMHO it means that the tube was manufactured and shipped in January 1944.

Except for the military dating code there is no real standard and each manufacturer may use their own system.

 

[raindownthunda]

Here is the reply I had from a professional tube tester I use. He rebuilds tube amps and tube testers for a living. This is in relation to 5998/WE421A.
But essentially relates to tubes in general.


“The PC/TC figures are pretty much a standard that people use to buy / sell valves to give an idea of their ‘goodness’, but in reality the 421A / 5998s are very high power triodes used mainly in Military applications back in the day, so to be honest for the purposes of matching the valves for your preamp, the PC score is really irrelevant, whether a valve can drive 90mA or 40mA is of no consequence when it is in circuit driving 5/6mA, they will pretty much all work until they become noisy or completely exhausted. A more useful parameter to match against is the TC (transconductance, loosely described as the gain of the valve), so use that as a basis for matching, but again don’t worry unduly, because I think you would be hard pushed to hear the difference between a valve with a TC of 9 or 14, but always good practice to get as close as possible. The main criteria with your amp I would suggest is how noisy they are, as that directly affects the listening experience, old valves can become noisy and microphonic, as you know”.

Yep, I can attest to this from personal experience in using power tubes in my BHC. I recently acquired a “low testing/below minimum good” WE 421A for a very, very cheap price. It tested something like 20 where 40 is ”min good” on TV7. It sounds exactly the same to my ears as another 421A I have that tests near NOS and is dead silent. Will it last as long? Probably not, but I’m rotating through other power tubes enough I would be surprised if it dies out any time soon.

I did get one low testing TS BGRP 6SN7 that is very microphonic and noisy, however I don’t know if this is correlated with the low test results. So YMMV but in my experience it’s worth gambling if you can get a good price- you’re likely to be pleasantly surprised.

 

[mordy]

Yep, I can attest to this from personal experience in using power tubes in my BHC. I recently acquired a “low testing/below minimum good” WE 421A for a very, very cheap price. It tested something like 20 where 40 is ”min good” on TV7. It sounds exactly the same to my ears as another 421A I have that tests near NOS and is dead silent. Will it last as long? Probably not, but I’m rotating through other power tubes enough I would be surprised if it dies out any time soon.

I did get one low testing TS BGRP 6SN7 that is very microphonic and noisy, however I don’t know if this is correlated with the low test results. So YMMV but in my experience it’s worth gambling if you can get a good price- you’re likely to be pleasantly surprised.

The WE tubes are known to be very long lasting.

 

[LobalWarming]

The WE tubes are known to be very long lasting.

That's what she said.

 

[JTbbb]

Yep, I can attest to this from personal experience in using power tubes in my BHC. I recently acquired a “low testing/below minimum good” WE 421A for a very, very cheap price. It tested something like 20 where 40 is ”min good” on TV7. It sounds exactly the same to my ears as another 421A I have that tests near NOS and is dead silent. Will it last as long? Probably not, but I’m rotating through other power tubes enough I would be surprised if it dies out any time soon.

I did get one low testing TS BGRP 6SN7 that is very microphonic and noisy, however I don’t know if this is correlated with the low test results. So YMMV but in my experience it’s worth gambling if you can get a good price- you’re likely to be pleasantly surprised.

This sounds beautiful, just like the NOS ones I have and is as quiet as a mouse. I know someone who would throw this in the bin!

 

[Isaacc7]

Wondering something, if someone buys the Tung-Sol 6SN7, 6F8G and 6J5 variants of the same year/plate will they sound the same or still have a variation in sound.

So far seems I'm on team TS and Melz. Not feeling Ken-Rads. RCA smoked glass is ok, but feels too blunted/warm. Thanks.

The consensus seems to be that the 6f8g and 6sn7 round plate black glass are the same thing. Tung Sol didn’t make a 6j5 with the same plate. There are round plate 6j5gt tubes labeled Tung Sol but they are actually Sylvania tubes. They are good tubes but don’t sound like the Tung Sol 6sn7.